Q. No.If \(\phi_1\) and \(\phi_2\) are the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip \(\phi\) is given by:
1. \(cos^2{\phi}=cos^2{\phi_1}+cos^2{\phi_2}\)
2. \(sec^2{\phi}=sec^2{\phi_1}+sec^2{\phi_2}\)
3. \(tan^2{\phi}=tan^2{\phi_1}+tan^2{\phi_2}\)
4. \(cot^2{\phi}=cot^2{\phi_1}+cot^2{\phi_2}\)
1. \(cos^2{\phi}=cos^2{\phi_1}+cos^2{\phi_2}\)
2. \(sec^2{\phi}=sec^2{\phi_1}+sec^2{\phi_2}\)
3. \(tan^2{\phi}=tan^2{\phi_1}+tan^2{\phi_2}\)
4. \(cot^2{\phi}=cot^2{\phi_1}+cot^2{\phi_2}\)
A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in the equilibrium state. The energy required to rotate it by \(60^{\circ}\) is \(W\). Now the torque required to keep the magnet in this new position is:
1. \(\dfrac{W}{\sqrt{3}}\)
2. \(\sqrt{3}W\)
3. \(\dfrac{\sqrt{3}W}{2}\)
4. \(\dfrac{2W}{\sqrt{3}}\)
A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from:
| 1. | the current source |
| 2. | the magnetic field |
| 3. | the lattice structure of the material of the rod |
| 4. | the induced electric field due to the changing magnetic field. |
| 1. | paramagnetic material only. |
| 2. | ferromagnetic material only. |
| 3. | paramagnetic and ferromagnetic materials. |
| 4. | diamagnetic material only. |
The following figures show the arrangement of bar magnets in different configurations. Each magnet has a magnetic dipole. Which configuration has the highest net magnetic dipole moment?
| 1. |  |
2. |  |
| 3. |  |
4. |  |
A bar magnet of length \(l\) and magnetic dipole moment \(M\) is bent in the form of an arc as shown in the figure. The new magnetic dipole moment will be:
| 1. | \(\dfrac{3M}{\pi}\) | 2. | \(\dfrac{2M}{l\pi}\) |
| 3. | \(\dfrac{M}{ 2}\) | 4. | \(M\) |
A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It:
1. will become rigid showing no movement
2. will stay in any position
3. will stay in north-south direction only
4. will stay in east-west direction only
| (i) | \(A\) is feebly repelled. | (ii) | \(B\) is feebly attracted. |
| (iii) | \(C\) is strongly attracted. | (iv) | \(D\) remains unaffected. |
Which one of the following is true?
| 1. | \(C\) is of a diamagnetic material. |
| 2. | \(D\) is of a ferromagnetic material. |
| 3. | \(A\) is of a non-magnetic material. |
| 4. | \(B\) is of a paramagnetic material. |
A vibration magnetometer placed in a magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of 2 s in the earth's horizontal magnetic field of 24 T. When a horizontal field of 18 T is produced opposite to the earth's field by placing a current-carrying wire, the new time period of the magnet will be:
1. 1 s
2. 2 s
3. 3 s
4. 4 s
Electromagnets are made of soft iron because soft iron has:
1. low retentivity and high coercive force
2. high retentivity and high coercive force
3. low retentivity and low coercive force
4. high retentivity and low coercive force
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